Readln; doesn't stop program from exiting

[RNBW]

It seems to work elsewhere, and worked before I put in the input line, but now after I have entered the number the program closes. 

Also, is there any way to stop 0 being displayed for the variable ns before entering its value?

Code: Pascal  [Select][+][-]

1. program SimpleBeam_Dev01_01;
2.  
3. {$mode objfpc}{$H+}
4.  
5. uses
6.   {$IFDEF UNIX}{$IFDEF UseCThreads}
7.   cthreads,
8.   {$ENDIF}{$ENDIF}
9.   Classes;
10.  
11.  
12. var
13.   ns,nl: Integer;
14.  
15. begin
16.    Writeln('SINGLE SPAN SIMPLY SUPPORTED BEAM PROGRAM');
17.    Writeln;
18.    Write('ENTER NUMBER OF SECTIONS TO BE CONSIDERED ON THE BEAM: ',ns);
19.  
20.    Readln;
21. end.
22.  

Any help will be appreciated.

[rvk]

How can I explain this without giving away too much

What do you think this line does?

Code: Pascal  [Select][+][-]

1. Write('ENTER NUMBER OF SECTIONS TO BE CONSIDERED ON THE BEAM: ',ns);

And what do you think this line does?

Code: Pascal  [Select][+][-]

1. Readln;

I don't see anywhere where you ask for input for the variable ns.
I see you outputting ns to the screen.
And I see you asking for the user to enter a (any) line.
But nothing about inputting ns.

[Handoko]

Well, some more hints for  RNBW:

ReadLn need parameter.
 

http://www.freepascal.org/docs-html/rtl/system/readln.html

--- edited:
Actually it needs 2 ReadLn: one with parameter and (the last) one without parameter.

[RNBW]

Thank you rvk and Handoko.

I completely misunderstood the Writeln('...', ns) in thinking that the ns would input the value, not display it.  Similar misunderstanding with Readln.

I've got it now and the code works fine.

[Thaddy]

ReadLn need parameter.
 

Yes, for it to be meanyningful it needs to be ReadLn(ns).
Readln always expects a #10 on linux, #13#10 on Windows, Dos, OS/2) as the last Keyboard entry for it to continue.

[Handoko]

@RNBW:

Glad to know you solved it.

Here are some good tutorials to improve your Pascal skill:
http://lazplanet.blogspot.co.id/
https://www.devstructor.com/
https://www.tutorialspoint.com/pascal/index.htm
http://wiki.freepascal.org/Lazarus_Documentation#Lazarus_and_Pascal_Tutorials

@Thaddy:

Thank you for the more detail info but I'm afraid the TS can't understand. But he sure will someday.

[RNBW]

Thank you Handoko for the list of tutorials.  I've already picked up a couple of them, but I'll have a look at the others.